Page:Popular Science Monthly Volume 46.djvu/487

Rh because they are so close that their light remains inextricably mingled after the highest practicable magnifying power has been applied in the effort to separate them. But the spectroscope



shows that the star is double and that its components are in rapid revolution around one another, completing their orbital swing in the astonishingly short period of four days! The combined mass of the two stars is estimated to be two and a half times the mass